Surface acoustic wave device and communication device

Abstract

A surface acoustic wave device includes front stage and rear stage surface acoustic wave elements, a signal wiring connecting between the front stage and rear stage surface acoustic wave elements, a reference potential wiring connected with the rear stage surface acoustic wave element and a capacitor made of an insulator interposed between the signal wiring and the reference potential wiring. A surface acoustic wave device includes a front stage surface acoustic wave resonator, a rear stage surface acoustic wave element, a signal wiring connecting between the front stage surface acoustic wave resonator and the rear stage surface acoustic wave element, a reference potential wiring connected with the rear stage surface acoustic wave element and a capacitor made of an insulator interposed between the signal wiring and the reference potential wiring. A communication device includes the surface acoustic wave device described above, a receiver circuit or a transmitter circuit.

1. A surface acoustic wave device comprising:
 a front stage surface acoustic wave resonator comprising an IDT electrode; 
 a first rear stage surface acoustic wave element and a second rear stage surface acoustic wave element connected in parallel through the first stage surface acoustic wave resonator, each of the first and second rear stage surface acoustic wave elements comprising three or more than three odd-number of IDT electrodes; 
 a signal wiring connecting between the IDT electrode of the front stage surface acoustic wave resonator and the IDT electrode of one of the first and second rear stage surface acoustic wave elements; 
 a reference potential wiring connecting between the IDT electrode of the one of the first and second rear stage surface acoustic wave elements and a reference electric potential electrode; 
 a capacitor comprising a portion of the signal wiring, a portion of the reference potential wiring facing the portion of the signal wiring and an insulator interposed between the portion of the signal wiring and the portion of the reference potential wiring; 
 an unbalance input/output terminal connected with the IDT electrode of the front stage surface acoustic wave resonator; and 
 two balanced output/input terminals each connected with the IDT electrode of each of the rear stage surface acoustic wave elements, respectively, 
 wherein a width of the portion of the reference potential wiring is different from a width of the portion of the signal wiring. 
 
   
   
     2. The surface acoustic wave device of  claim 1 , wherein the insulator comprises silicon oxide or polyimide resin. 
   
   
     3. The surface acoustic wave device of  claim 2 , wherein the insulator comprises a particle of an insulative material that has a dielectric constant different from a dielectric constant of the insulator, or the insulator comprises a particle of a metal. 
   
   
     4. The surface acoustic wave device of  claim 1 , wherein the reference electric potential electrode comprises an annular electrode formed to surround the front stage surface acoustic wave resonator, the first and second rear stage surface acoustic wave elements, the signal wiring, the reference potential wiring, the capacitor, the unbalanced input/output terminal and the balanced output/input terminals. 
   
   
     5. The surface acoustic wave device of  claim 1 , wherein one of the first and second rear stage surface acoustic wave elements is provided with the reference potential wiring. 
   
   
     6. The surface acoustic wave device of  claim 1 , wherein the first rear stage surface acoustic wave element is provided with the reference potential wiring that forms one of the capacitor and the second rear stage surface acoustic wave element is provided with the reference potential wiring that forms another of the capacitor. 
   
   
     7. The surface acoustic wave device of  claim 6 , wherein materials of the insulators forming the two capacitors are different from each other. 
   
   
     8. The surface acoustic wave device of  claim 6 , wherein widths of the insulators forming the two capacitors are different from each other. 
   
   
     9. A communication device comprising the surface acoustic wave device of  claim 1 , comprising:
 a mixer for mixing a transmission signal with a carrier signal to generate an antenna transmission signal; 
 a band-pass filter comprising the surface acoustic wave device and attenuating an unnecessary signal in the antenna transmission signal; and 
 a power amplifier amplifying the antenna transmission signal and outputting the amplified antenna transmission signal to an antenna through a duplexer. 
 
   
   
     10. A communication device comprising the surface acoustic wave device of  claim 1 , comprising:
 an antenna; 
 a low noise amplifier amplifying an antenna reception signal that has been received by the antenna and has passed through a duplexer; 
 a band-pass filter comprising the surface acoustic wave device and attenuating an unnecessary signal in the antenna reception signal amplified by the low noise amplifier; and 
 a mixer separating a reception signal from a carrier signal in the antenna reception signal that has passed through the band-pass filter. 
 
   
   
     11. A surface acoustic wave device comprising:
 a front stage surface acoustic wave element comprising three or more than three odd-number of IDT electrodes; 
 a rear stage surface acoustic wave element comprising three or more than three odd-number of IDT electrodes; 
 a signal wiring connecting between the IDT electrode of the front stage surface acoustic wave element and the IDT electrode of the rear stage surface acoustic wave element; 
 a reference potential wiring connecting between the IDT electrode of one of the front and rear stage surface acoustic wave elements and a reference electric potential electrode; 
 a capacitor comprising a portion of the signal wiring, a portion of the reference potential wiring facing the portion of the signal wiring and an insulator interposed between the portion of the signal wiring and the portion of the reference potential wiring; 
 an unbalance input/output terminal connected with the IDT electrode of the front stage surface acoustic wave element; and 
 two balanced output/input terminals each connected with one of the IDT electrodes of the rear stage surface acoustic wave element, 
 wherein a width of the portion of the reference potential wiring as different from a width of the portion of the signal wiring. 
 
   
   
     12. The surface acoustic wave device of  claim 11 , wherein the insulator comprises silicon oxide or polyimide resin. 
   
   
     13. The surface acoustic wave device of  claim 12 , wherein the insulator comprises a particle of an insulative material that has a dielectric constant different from a dielectric constant of the insulator, or the insulator comprises a particle of a metal. 
   
   
     14. The surface acoustic wave device of  claim 11 , wherein the reference electric potential electrode comprises an annular electrode formed to surround the front and rear stage surface acoustic wave elements, the signal wiring, the reference potential wiring, the capacitor, the unbalanced input/output terminal and the balanced output/input terminals. 
   
   
     15. The surface acoustic wave device of  claim 11 , further comprising another of the capacitor, wherein materials of the insulators forming the two capacitors are different from each other. 
   
   
     16. The surface acoustic wave device of  claim 11 , further comprising another of the capacitor, wherein widths of the insulators forming the two capacitors are different from each other. 
   
   
     17. A communication device comprising the surface acoustic wave device of  claim 11 , comprising:
 a mixer for mixing a transmission signal with a carrier signal to generate an antenna transmission signal; 
 a band-pass filter comprising the surface acoustic wave device and attenuating an unnecessary signal in the antenna transmission signal; and 
 a power amplifier amplifying the antenna transmission signal and outputting the amplified antenna transmission signal to an antenna through a duplexer. 
 
   
   
     18. A communication device comprising the surface acoustic wave device of  claim 11 , comprising:
 an antenna; 
 a low noise amplifier amplifying an antenna reception signal that has been received by the antenna and has passed through a duplexer; 
 a band-pass filter comprising the surface acoustic wave device and attenuating an unnecessary signal in the antenna reception signal amplified by the low noise amplifier; and 
 a mixer separating a reception signal from a carrier signal in the antenna reception signal that has passed through the band-pass filter.